feat: consume reservation samples

[BigBlackWolf]

Description

Samples, which demonstrates how to create reservation, which can be consumed by:

• any instance
• instance, which should specify exact reservation

doc link: https://cloud.google.com/compute/docs/instances/reservations-consume

Note: Before submitting a pull request, please open an issue for discussion if you are not associated with Google.

Checklist

• I have followed Contributing Guidelines from CONTRIBUTING.MD
• Tests pass: go test -v ./.. (see Testing)
• Code formatted: gofmt (see Formatting)
• Vetting pass: go vet (see Formatting)
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample
• Please merge this PR for me once it is approved

[snippet-bot]

Here is the summary of changes.

You are about to add 2 region tags.

• compute/reservations/consume_any_reservation.go:17, tag compute_consume_any_matching_reservation
• compute/reservations/consume_specific_reservation.go:17, tag compute_consume_single_project_reservation

---

This comment is generated by snippet-bot.
If you find problems with this result, please file an issue at:
https://github.com/googleapis/repo-automation-bots/issues.
To update this comment, add snippet-bot:force-run label or use the checkbox below:

• Refresh this comment

[telpirion]

There are a couple core issues with this PR:

1. There is more than one function per region tag
2. It looks like there is a lot of duplication with existing samples.

See:
https://github.com/GoogleCloudPlatform/golang-samples/blob/main/compute/reservations/create_reservation.go

[telpirion]

issue: it looks like you're duplicating the same code, createConsumableReservation() twice. Let's not do that. If the snippet needs this to run, then put all of this code into the test file.

[BigBlackWolf]

I've done it in this way, to be as close as possible to the gcloud example in documentation.
There it is done in 2 steps:

1. shows how to create a reservation (yeah, in this case, consuming any reservation, it just duplicates existing sample)
2. actual consuming

Therefore, I thought it would be consistent to keep 2 functions. Do you think it's better to remove first and keep only consumeAnyReservation()?

[telpirion]

issue: same as previous. If this function is required as a snippet, it should be in its own code file.

See: https://googlecloudplatform.github.io/samples-style-guide/#one-per-file

Also, it looks very similar to createConsumableReservation(). Is there any code that makes it unique compared to the other function.

[BigBlackWolf]

Thanks for pointing out, but here is the same situation. In gcloud example it is separated into 2 steps, but this is still a single sample.

Is there any code that makes it unique compared to the other function.

Yes, there is additional field, which makes the difference to consuming
SpecificReservationRequired: proto.Bool(true)

I can make all actions being made in a single function, will it be better?